Antennas and other sensors used in radar systems for example, typically utilize a large area antenna array (e.g. a radio frequency beam scanning array) mounted on a rotating platform to revolve the antenna in the azimuth direction. These rotatable platforms allow the array to be oriented at a particular azimuth angle, or to sweep through an entire range of azimuth angles at a predetermined angular rate. In traditional rotating radar systems, one end of the array is pivotally mounted to the rotating platform, forming a cantilevered arrangement in which the array may be, for example, oriented in a stowed or transport position, or oriented at a target elevation angle by means of one or more actuators.
The actuators used to elevate these types of antenna arrays may comprise linear ball screw actuators driven by electric motors. While accurate in operation, one disadvantage of this type of actuator results from the inability to “float” (or unload) the actuator when in the stowed or transport position, as is conventionally achievable with other linear actuator types, such as linear hydraulic actuators. As a result, the load paths of the antenna structure become statically indeterminate and otherwise difficult to evaluate, adding a level of uncertainly to the design of the structure.
Referring generally to FIG. 1, a scanning antenna array system 10 is shown, including a base 11 and an antenna array 12 pivotally mounted to a rotating pedestal 15 about pivot point 14. The elevation angle of array 12 may be altered via linear actuator 18 pivotally connected to array 12 at pivot point 19, and to pedestal 15 at pivot point 16. As shown, system 10 is in a stowed or transport position, wherein the inability to float actuator 18 results in statically indeterminate load paths (three fixed points illustrated). The inability to accurately calculate potential loads on the array and support structure is currently addressed by adding additional structural elements to provide added support to the system. This potentially excessive strengthening increases system weight, as well as requires the use of additional sensors, interlocks and software to more closely monitor actuator position and performance.
Improved systems and methods are desired.